| Summary: | Detailed analysis of the influence of cloudiness on extreme air temperatures and diurnal temperature ranges (DTR) in the Arctic in 1951-1990 is presented. This analysis is preceded by a description of a cloudiness fluctuation and trends in the Arctic during the last decades. A statistically significant increase of the mean cloudiness in the Arctic occurred in winter, spring and during a year. It could be due to incursion of a polluted air to the Arctic from the lower latitudes. An overall pattern of the influence of cloudiness on the daily maximum air temperature (TMAX) and the minimum air temperature (TMIN) is roughly similar. However, sometimes there are significant differences in the anomalies for clear, partly cloudy and cloudy days. In summer even an opposite influence of cloudiness on TMAX than on TMIN was noted for the Norwegian Arctic and the southern Canadian Arctic. Relations between cloudiness and DTR, based on daily data, entirely confirm the previous conclusions based on monthly data. Therefore, an increasing cloudiness of the last decades significantly influences a decrease of DTR in die Arctic, especially during the warm half-year when a solar radiation is present. During the cool half-year (particularly at polar night) an influence of cloudiness is clearly weaker and not univocal, and probably less important than non-periodical day-to-day changes of air temperature, governed at this time by very vigorous atmospheric circulation.
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